1. Field of the Invention
The present invention relates to an aluminum alloy for a tough, die-cast product and particularly, an Al--Mg--Mn--Ni based alloy.
2. Description of the Related Art
Aluminum alloys are known from which a die-cast product having a relatively high strength in an as-cast state can be produced (for example, see Japanese Patent Application Laid-open No. 63-250438).
Attempts are presently being made to substitute die-cast products made of an aluminum alloy for various parts made of steel due to a demand for decreasing the weight of a motorcycle. In this case, the die-cast product must have not only high strength but also excellent shock resistance, that is, the die-cast product should have a high toughness for the reason that various parts are exposed to the outside.
It is also required that when the die-cast product is subjected to an anode oxidizing treatment in order to enhance the appearance quality of the motorcycle, the film formed on the resulting product should be aesthetically appealing.
A conventional die-cast product made of aluminum alloy has the advantages that it can be placed into use in an as-cast state, thermal treatment can be eliminated to enhance productivity and production costs can be reduced. However, the conventional die-cast product suffers from the problem that because the Ni content is as high as in the range of 1% by weight.ltoreq.Ni.ltoreq.5.5% by weight, grains of an acicular intermetallic compound, AlMnNi, are liable to be coalesced, and due to this, the toughness of the die-cast product is relatively low, and the aesthetic aspect of the film formed by the anode oxidizing treatment may also be reduced.